1. Field of the Invention
The present invention relates to a pyrophoric sheet, processes for its manufacture, and its use as an infrared decoy device. The pyrophoric sheet can utilize the heat generation accompanying the oxidation of iron with oxygen in air. The present invention also relates to such a pyrophoric sheet that contains an additive that reduces the stiction between adjacent sheets when the sheets are packed into a container and subsequently ejected from the container, and a method of producing the same, and its use as an infrared decoy device.
2. Description of the Related Art
Heat generating devices can be ejected from vehicles and aircraft to divert heat-seeking missiles away from a target and/or to disrupt heat-seeking missiles from locking onto a target. These infrared-generating devices contain a payload that heats to a predetermined temperature when the device is functioned. One type of infrared-generating device utilizes pyrotechnic payloads to produce high temperatures (>1000° C.). Another type of payload employs pyrophoric materials that ignite spontaneously when exposed to atmospheric oxygen. Pyrophoric materials can be designed to function at lower temperatures than pyrotechnic materials, which reduces the visible signature from the device and increases the operational covertness.
To maximize the effectiveness of a pyrophoric infrared decoy it is desirable to generate a heat emitting cloud that has a large infrared emitting cross section. One method of increasing the cross section is to process the pyrophoric materials into thin sheets (coupons) that are stacked into a container. Upon ejection, the coupons separate and heat, forming an infrared emitting cloud with a large cross section.
U.S. Patent Application No. 20090050245 discloses a process for producing a pyrophoric material in which metal carboxy compounds are coated onto a combustible substrate such as cloth. The coated substrate is heated in an oxygen free atmosphere to render the substrate pyrophoric. The method of fabricating a pyrophoric material where the pyrophoric pre-cursor is applied to an existing substrate has limitations associated with the types of substrates that can be utilized as a support matrix, the loading levels and distribution of the particles within the substrate, and the production throughput.
U.S. Pat. No. 7,749,357 discloses a papermaking process to fabricate a heat generating molded sheet that contains an oxidizable metal, a moisture retaining agent, and a fibrous material. The molded sheets are described as utilizing an iron powder that has dimensions of microns and, in the presence of an electrolyte solution, heats over a period of minutes. This technique does not produce a heated sheet with a sufficiently high temperature to perform as an infrared decoy.
Accordingly, an object of the present invention is to provide a heat generating sheet that when ejected from a device provides a large infrared cross section that will be effective as a decoy from a heat seeking missile and a method of producing the infrared heating elements.